Pressure exchangers



June 14, 1960 D. B. SPALDING PRESSURE EXCHANGERS Filed Feb. 24, 1956 PRESSURE EXCHANGERS Dudley Brian Spalding, 2, Vineyard Hill Road, SW. 19, Wimbledon, London, England Filed Feb. 24, 1956, Ser. No. 567,648

Claims priority, application Great Britain Mar. 10, 1955 7 Claims. (Cl. 230-69) The invention relates to pressure exchangers and particularly to a method of producing compressed gas from such machines. Pressure exchangers are known machines having cells for the compression and expansion of gas, ducting to lead gas to and from the cells at difierent stages of operation, and means to effect cyclic communication between the cells and the ducting.

It has been previously proposed to compress a gas, for example air, in the cell-wheel of a pressure exchanger by the introduction of high pressure gas into cells containing low pressure air. The air is then compressed by the direct action of the high pressure gas during the process of pressure equalization in the cell. The high pressure gas, which may be heated air, is led to the cells by suitable ducting, and the compressed air led from the cells by further ducting. .The supply of compressive high pressure hot gas in such apparatus has been provided from a heating system external to the cells.

According to the present invention there is provided a method of compressing gas by means of a pressure exchanger in which a part of the gas admitted to a cell thereof during an inlet stage is subjected to compression in that cell as a resultant efiect of combustion in another part of the gas admitted at the same inlet stage.

A pressure exchanger operable to perform this method preferably has fuel injection means located adjacent one wall of the inlet duct so that fuel is injected into the other part of the gas. The fuel/ gas mixture may be so admitted that it has a tendency to remain at the inlet end of the cells. Thereafter a cell may encounter in turn ignition means at the inlet duct end followed by a gas delivery duct and an exhaust duct at the opposite end. A transfer ted States Patent passage may be incorporated which straddles cells passing the ignition means and the gas delivery duct and which communicates with said opposite end of the cells.

Embodiments of the invention will now be described with reference to the accompanying diagrammatic drawings, of which:

Figure l is a peripheral development of a pressure exchanger cell rotor shown in relation to stationary ducts.

Figure 2 shows a modified form of the Figure 1 arrangement incorporating a single transfer passage and making use of wave processes.

In Figure 1, the developed cell-wheel 1 moves in the direction of the arrow 2 between end-plates 3 and 4. Consider a single cell at the position 5. This is being filled with fresh air which is admitted through the duct 6 in a manner described later. Part of the air passing through a port 19 terminating the duct 6 receives fuel from a spray injector 7 mounted in a wall portion 22 forming a part of the inlet duct 6 and situated adjacent to the end-plate 4 considering the direction of cell movement. The resulting fuel-air mixture enters the cell just before it is closed by the edge 8 of the duct. The fuel is injected by stratification in the direction of the flow through the duct so that it does not spread across that flow; rather it is constrained to alfect only a part of the flow cross-section. In fact the spread of fuel may be Patented June 14, 1960 "ice prevented if necessary by a partition in the duct. The cell at position 9 now contains fresh air together with a fuel-air mixture at its upstream end. The path of the boundary between air and mixture is shown by an irregular line. The mixture is ignited as the cell passes a glowplug 10 mounted in the endplate, and its pressure and volume are increased during combustion. The fresh air is compressed in the downstream region of the cell, and subsequently expelled through a port 26 terminating the delivery duct 11. The closing of this duct is timed and the duct pressure arranged to prevent the escape of combustion gases from the cell. These gases remain in the cell until it communicates with a port 21 terminating the exhaust duct 12, through which they expand, leaving a depression in the cell which encourages the flow of fresh air into the cell through the inlet duct 6. The cycle for that cell then commences again.

When two gases at different pressures are suddenly brought together, as when a cell of a pressure exchanger communicates with a duct carrying gas at a pressure different from that of the gas in the cell, a wave or impulse is set up and travels through the cell at about sonic velocity. This may be a compression or expansion wave, depending on whether the cell pressure is lower or higher than that of the duct. Pressure exchangers have been designed in which performance is enhanced by making use of these waves, and improvement has also been ob tained by the use of pressure-transfer passages. The efficiency of the process described above may be similarly improved, and Figure 2 shows how the simple apparatus of Figure 1 may be modified to obtain these improvements.

In the example of Figure 2, the construction and operation of the cells and ducting are related to the gas movements in a known manner, so that effective use is'made of the compression and expansion waves to assist the filling and emptying of the cells respectively. The paths of compression Wave fronts, relative to the stationary ducting, are shown by full lines. Those of expansion wave fronts are shown by the dotted lines.

The emptying of a cell into the exhaust duct 12 is now assisted by an expansion wave 13 which travels through the cell and sets up a powerful depression at its upstream end. The inlet duct is then opened to the cell, which is rapidly filled with fresh air as the exhaust gases escape to duct 12. The exhaust duct is then closed by further movement of the cell, and a compression wave is set up, travelling towards the open end of the cell and causing a build-up of pressure in the fresh charge. The cell is then closed by the edge 8 of the inlet duct. Under design operating conditions, a considerable degree of supercharging of the cell may be obtained, and in this way some of the energy contained in the exhaust gases can be recovered, and the mass flow through the machine increased.

The compression of the cell contents before combustion is further effected by the re-circulation of previously compressed air through a transfer passage 14. This process is also improved by the expansion and compression waves 15 and 16. Each wave travels through the cells, setting the cell contents in motion, and is reflected from the endplate 4. The reflected waves 17 and 18 travel back towards the open end of the cells, bringing the contents of the cells to rest in respectively expanded and compressed conditions. A cell which has been pre-compressed in this manner then reaches the ignition plug 10, and the combustion of the fuel-air mixture sets up a series of small compression waves (not shown), which travel through the cell at a greater speed than the expanding gases, compressing the air at the other end of the cell. The cell is then opened to the delivery duct, which is at a somewhat lower pressure than that of the cell. The delivery of the single cell Wheel, so that each cell undergoes several cycles for one revolution of .the 'cell Wheel. The alternative means of producing relative rotation between cells and ducting, which has been previously disclosed, could also be employed in carrying out the present invention, i.e. the cells could be stationary with the. ductingrotatable. The air'can be compressed in several stages by passing it from one cell wheel to another, or by a multiplicity of pressure-transfer passages. I a a H If the compressed air is requiredto operate a turbine or process, or for jet-propulsion purpo'sesgand to ,be heated, this may be done continuously or intermittently, asrequired, in an external combustion chamber. Alternatively, by a suitable fuel supply and duct arrangement, air leaving the delivery duct 11 may containa substantial proportion of hot combustion gases. In such an arrangement, the necessity for a separate exhaust duct may be eliminated. What I claim:

'1. A pressure exchanger comprising an open-ended cell rin end closure means for the cells, inlet, delivery and exhaust ducts, and means for ettecting rotation of the cell relative to' said ducts, said'inlet duct providing a gas flow path into the cells, said'delivery duct and said exhaust duct each providing a gas flow path out of the; cells, the exhaust duct being arranged in the direction of relative rotation before the inlet duct and the delivery, duct being arranged in the direction of relative rotation after the inlet duct, fuel injection means mounted in vclose V proximity to the cell ring and adjacent the side of said inlet duct nearer to the delivery duct in the direction of relative rotation directed to inject fuel into a part only of the gas flow path and ignition meanspositioh'ed inlth'e end closure means to communicate successively with each of the cells to ignite the fuel-containing part of the gas. v 2. A pressure exchanger as claimed in claim 1, in which theexhaust duct is slightly offset with respect to the inlet duct. j

3; A pressure exchanger as claimed in claim 1,'in which the inlet duct is connected to a port in one end closure means 'and the delivery and exhaust ducts are each connected to ports in the other end closuremean's. f

4. A pressure exchanger as claimed in claim 1, in which a transfer passage is provided, one end of the passage communicating with a cell between the inlet duct and the ignition means and the other end of the passage with a een between the delivery duct and theexhaust duct.

5. A pressure exchanger as claimed in claim 1; in which said fuel injection means is disposed in a wall portion forming a part of the inlet duct and situated adjacent to the said end closure means with respect to the direction of rotation of the cell ring.

6. A pressure exchanger comprising a series of openended cells arranged in annular-;form, end-plates closing the ends of said cells, means for effecting relative rotation between said cells and-said end-plates and an inlet ductconnected to one of said end -platesand providing a gas flow path intofthe ceills, a'delivery duct and an exhaust duct connected to the other of said end-plates and each providing ag a's flowpathout of the-cells the exhaust duct being slightly ofisetcircum ferentially and arranged in the direction of rotation before the inlet duct and the delivery duct circumferentially spaced and arranged in the direction of rotation after the inlet duct, fuel injection means mounted in close proximity to the cells and adjacent the side of said inlet duct nearer to the, delivery-duct in the direction of relative rotation directed to inject fuel by Stratification into a part only of the gas flow path into the cells andig'nitionmeans arranged in said one end plate and positionedto communicate successively with each of th'ecells aftera cell has communicated with the inlet duct and before it communicates with the delivery duct.

7 7. A pressure exchanger comprising a series. of openended cells arranged in annular form, end plates closing the end ofsaid cells, means for efiecting relatiyerotation direction of rotation before the inlet duct and the delivery duct circumfere'ntially spaced. and arranged in the direction of,rotation' after the inlet duct, fuel injection means mounted in close proximity to the cells and adjacent the side of said inlet duct nearer to the ,delivery duct in the direction of relative rotation. directed to inject fuel by stratification' into a part only of the gas flow path into the cells and ignition means arranged in said one end plate and positioned to communicate successively with each of the cells after a cell has communicated with the inlet duct and before it communicates with the delivery duct References Cited in the file of this patent UNITED STATES PATENTS an, War 

